Agricultural tractors are used in combination with implements which are towed by the tractor. A tractor/baler combination is used in agriculture to take up crop lying or standing on a field and to press and bind it to a bale. A tractor/baler combination with automatically controlled operations is described in U.S. Pat. No. 7,404,355, issued in July 2008 and assigned to the assignee of the present application.
When a tractor is operating in the field with an external implement, such as a baler, determining and controlling the speed, it is often necessary for the operator to make temporary adjustments to the speed of the tractor. At the same time, it is not preferable to require the operator to take an explicit action to re-initiate automation after making one of these frequent adjustments. On the other hand, the operator should have the ability to take over full manual control quickly and intuitively. For example, while baling, an operator often needs to slow the vehicle down due to field conditions, such as a “rut” or a heavy windrow that the automatic speed control system cannot respond to quickly enough, and then return control to the automated system. A similar situation can occur with a tractor following a combine. But, when a combine unload operation is completed, the operator often wants to take full control of the speed as the tractor pulls away from the combine.